Needle clamp screw thread

[edbell1925]

Hi

I have recently purchased an early Edison Bell magnetic pickup (cat No407), but the needle clamp screw is missing. It needs to be at least .25inch (6mm) long but I cannot determine the thread. An EB sound box screw seems too big a diam. and a BA screw goes in a little way then jams!

Has anyone any ideas what it is or where I might obtain one.

Thanks for any help you can give

Best regards
Edbell1925